trans alt and trans level, QNH and QNE

D

davidhigbie

Well-Known Member
I've got the rote definitions of trans alt and trans level down with a good deal of understanding BUT how do QNH and QNE relate?



Is this right: Trans Alt= QNH and Trans Level= QNE? (jeppesen says it is this way, "everything explained for the prof pilot" seems to indicate the opposite?!?)



It seems as if QNH and QNE appear on enroute charts and Trans Alt and Trans Level appear only on approach plates, is this correct?

Any comments would be helpful...
 
Hey Dave,

Transition Altitude is the alitude when you're climbing when you'll swith to QNE (29.92)

Transition Level is the FL on the way down when you'll switch to a local altimeter setting known as QNH.

QNE = 29.92
QNH = Local altimeter setting

Hope I'm right!
 
Sounds right...think of...

QNH as QN"home" or local field altimeter
QNE as EXTERNAL or outside and 29.92.
 
Hmm, always heard Qne as "enroute".

Transition altitude is the highest altitude you can legally fly (unique to each country) using Qnh or Qfe setting (many countries use Qfe below transition altitude).

Transition Level is, essentially, the lowest useable or legal flight level.
 
Wouldnt using QFE below trans alt be relatively inaccurate, especially over changing terrain? Kind of like a poor man's radar alt which never changes?


Yep, QNH = "home" and QNE = "enroute"...I had come up with "eagle" but "enroute sounds better". Why dont they just say trans alt or trans level or QNE or QNH instead of both?
 
You use the airport elevation for setting Qfe. Sure, the aircraft's absolute altitude is changing as you fly over terrain, but it does provide for an accurate idea of how high off the touchdown point you are. It works, just a different philosophy. Many airlines used it until recently, including EAL and AAL. The latter changed more due to the FMS issues than anything else.

As for the terms, Qnh, Qfe and Qne refer to the altimeter setting, while transition altitude/level refers to where you use what. You need both terms.
 
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